The highest day temperature in September 2023 was 79°F. The lowest night temperature was 38°F. The average values for day and night temperatures during September were 67.8°F и 50.5°F respectivly.

Most of the days in September are sunny but you can also expect cloudy and gloomy days.

Precipitation total in September for Boulder is 0.9 in.

The average wind speed in September is 6.5 mph. This value is relatively stable throughout the year.

We are using day length and cloud cover information for each day of the month to calculate averages for this chart. Average sunny hours for Boulder in September is 9.5 hours.